Department of Biochemistry and Cell Biology, Geisel School of Medicine at Dartmouth, Hanover, United States.
Norris Cotton Cancer Center, Lebanon, United States.
Elife. 2017 Nov 20;6:e29303. doi: 10.7554/eLife.29303.
The fidelity of chromosome segregation in mitosis is safeguarded by the precise regulation of kinetochore microtubule (k-MT) attachment stability. Previously, we demonstrated that Cyclin A/Cdk1 destabilizes k-MT attachments to promote faithful chromosome segregation. Here, we use quantitative phosphoproteomics to identify 156 Cyclin A/Cdk1 substrates in prometaphase. One Cyclin A/Cdk1 substrate is myosin phosphatase targeting subunit 1 (MYPT1), and we show that MYPT1 localization to kinetochores depends on Cyclin A/Cdk1 activity and that MYPT1 destabilizes k-MT attachments by negatively regulating Plk1 at kinetochores. Thus, Cyclin A/Cdk1 phosphorylation primes MYPT1 for Plk1 binding. Interestingly, priming of PBIP1 by Plk1 itself (self-priming) increased in MYPT1-depleted cells showing that MYPT1 provides a molecular link between the processes of Cdk1-dependent priming and self-priming of Plk1 substrates. These data demonstrate cross-regulation between Cyclin A/Cdk1-dependent and Plk1-dependent phosphorylation of substrates during mitosis to ensure efficient correction of k-MT attachment errors necessary for high mitotic fidelity.
在有丝分裂过程中，染色体分离的保真度通过动粒微管（k-MT）附着稳定性的精确调节来保证。此前，我们证明了周期蛋白 A/Cdk1 使 k-MT 附着不稳定，从而促进忠实的染色体分离。在这里，我们使用定量磷酸化蛋白质组学来鉴定前期的 156 个周期蛋白 A/Cdk1 底物。周期蛋白 A/Cdk1 的一个底物是肌球蛋白磷酸酶靶向亚基 1（MYPT1），我们表明 MYPT1 向动粒的定位取决于周期蛋白 A/Cdk1 的活性，并且 MYPT1 通过负向调节动粒处的 Plk1 来使 k-MT 附着不稳定。因此，周期蛋白 A/Cdk1 磷酸化使 MYPT1 能够与 Plk1 结合。有趣的是，在 MYPT1 耗尽的细胞中，Plk1 自身（自我引发）对 PBIP1 的引发增加，表明 MYPT1 在 Cdk1 依赖性引发和 Plk1 底物的自我引发过程之间提供了分子联系。这些数据表明，在有丝分裂过程中，周期蛋白 A/Cdk1 依赖性和 Plk1 依赖性底物磷酸化之间存在交叉调节，以确保对动粒微管附着错误进行有效的校正，从而保证高有丝分裂保真度。
